Some smokers who quit really put on the pounds afterward. Now, scientists have discovered that smokers who have a specific variant of a gene may be more likely to overeat after quitting and that the drug Zyban curbs their urge to eat too much.

This is one of the first studies to show that some people may be genetically predisposed to overeat after they stop smoking. The hope is that, eventually, doctors could screen smokers for the gene variant to identify those who are most prone to weight gain after quitting and therefore most likely benefit from drugs such as Zyban.

There is not a gene test currently available and it could be several years before one comes on the market.

“Using genetic information we might be able to someday individualize treatments for smoking cessation,” say Caryn Lerman of the University of Pennsylvania, Philadelphia, who led the study. She cautions that the findings would have to be confirmed in larger studies before doctors would begin tailoring cessation treatments based on genetics.

Weight gain after quitting smoking is a fairly common and serious health problem. Roughly 75 percent of smokers gain weight after quitting cigarettes, and a quarter of those who quit gain more than fifteen pounds in the first year.

Lerman and her colleagues found that among smokers who quit successfully, those with a specific gene variant were more likely to choose food as a reward than those without the gene variant were. Treating these smokers with Zyban made them less likely to choose food after quitting than those who received a sugar pill.

“These results provide new evidence that the increase in body weight that occurs following smoking cessation is related to increases in food reward, and that food reward is partly determined by genetic factors,” the authors write in Psychopharmacology.

The variant occurs in a gene called DRD2, which regulates the amount of dopamine in the brain, and it is thought that Zyban somehow makes more dopamine available in the brain.

The study was relatively small and included 71 smokers who were evaluated on their urge to eat before and after quitting smoking.